YouTube has a feature where you can transition to and from full screen video on YouTube. Unfortunately, the feature has a performance flaw where there is a lag while entering and leaving full screen. This is a result of YouTube moving the heavy fluff around the DOM when switching to and from full screen.

This extension solves this problem by hiding the fluff while transitioning.

The performance of this extension is great when used with a small number of videos. It also works well with large lists of videos and will not cause lags on pages with lots of ads, videos and/or comments.